JPH11228155A - Method for heating optical element forming mold and apparatus there for - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce unequal heat distribution which occurs at the time of forming optical elements. SOLUTION: In the heating method for optical element forming molds for heating a pair of the forming molds 1, 2 arranged with forming surfaces la, 2a to face each other and an optical element blank 3 arranged between these forming molds 1, 2 by the electromagnetic waves oscillated from radiation heating means 13; reflection mirrors 15 which reflect the electromagnetic waves oscillated from the radiation heating means 13 are moved, by which the focal position of the electromagnetic waves or the reflection direction of the electromagnetic waves are changed to control the radiation heat quantity arriving at the forming molds 1, 2 between the one forming mold 1 and the other forming mold 2. Heating is executed while a temp. difference is generated between a pair of the forming molds 1 and 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating means for an optical element molding die in a method for molding a glass optical element,
More specifically, the present invention relates to a method and an apparatus for heating an optical element mold using radiation heating means.

[0002]

2. Description of the Related Art Conventionally, as a method of heating an optical element mold using a radiation heating means, a technique disclosed in Japanese Patent Application Laid-Open No. 62-59539 is disclosed as "a heating method in pressure molding of an optical element". Have been. This technique will be described with reference to FIG. In FIG. 10, a furnace wall 102 is formed on an inner peripheral wall of the pressure molding device 101. Side wall 1 of furnace wall 102
02a, a reflecting plate 103 is attached by an appropriate means.
4 can be attached. In the center of the pressure molding apparatus 101, a body mold 106a, an upper mold 106b, and a lower mold 106c of a mold 106 for pressure molding are provided on a holding table 105. A molding material 107 is previously placed in a pressure molding chamber 106d of the molding die 106. A pressing rod 108 is fixed to the upper die 106b of the mold 106. The pressing rod 108 is pushed down by driving a pressing rod driving means (not shown). That is, when the pressure rod 108 is pressed down, the upper mold 10
6b is pushed down, and the molding material 107 in the pressure molding chamber 106d is compression molded.

Next, a method for heating the molding die 106 and the molding material 107 using the pressure molding apparatus 101 will be described. The heat rays emitted from the halogen lamp 104 are reflected by the reflection plate 103 into the body mold 10 of the molding die 106.
6a is concentrated on the insertion portion of the molding material 107. The heat of the heated portion is transmitted to the molding material 107 more than is transmitted to the upper die 106b and the lower die 106c of the molding die 106. Therefore, the molding material 107 is softened by heating with less heat energy and faster than in the conventional heating method, so that pressure molding can be performed. On the other hand, the temperatures of the upper mold 106b and the lower mold 106c at the time when the molding material 107 is heated and softened are lower than those of the conventional heating method. No bubbles are generated on the optical surface where the material 106c contacts the molding material 107.

[0004]

However, the above prior art has the following problems. That is, if there is a remarkable difference in the radius of curvature of optical elements such as lenses,
When the upper mold and the lower mold of the molding die are uniformly irradiated with radiant heat and molded, during the molding process of the optical element, for example, the glass volume filling the cavity of the upper mold having a small radius of curvature is reduced. However, since the volume of glass filling the lower mold cavity having a large radius of curvature is larger, the glass filling the upper mold cavity has a higher heat capacity than the glass filling the lower mold cavity. And the cooling of the glass on the upper mold side becomes slower when cooling the glass. For this reason, uneven heat distribution is generated in the molded optical element, and internal stress is generated, causing problems such as sink marks, cracks, and occurrence of birefringence due to residual stress.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide an optical element molding die for reducing uneven heat distribution generated when molding an optical element. Is to provide a heating method. An object of the invention according to claim 2 is to provide a heating device for an optical element molding die for implementing the method for heating an optical element molding die according to claim 1 of the invention.

[0006]

According to a first aspect of the present invention, there is provided a method of heating an optical element mold, comprising: a pair of molds having molding surfaces opposed to each other; In a heating method of an optical element molding die for heating an optical element material disposed between molds by electromagnetic waves oscillated from a radiation heating means, by moving a reflecting mirror for reflecting the electromagnetic waves oscillated from the radiation heating means. By changing the focus position of the electromagnetic wave or the reflection direction of the electromagnetic wave, the amount of radiant heat reaching the mold is controlled to be different between the one mold and the other mold, and a temperature difference is generated between the pair of molds. And heat. The heating device for an optical element forming die according to the second aspect of the present invention oscillates a pair of forming dies whose forming surfaces are opposed to each other and an optical element material disposed between the forming dies from the radiation heating means. In a heating device of an optical element molding die for heating by an electromagnetic wave, a reflecting mirror for reflecting the electromagnetic wave oscillated from the radiant heating means, and a variable means for changing a position or a rotation angle of the reflecting mirror in an optical axis direction are provided. I do.

That is, in the heating method of the optical element molding die according to the first aspect of the present invention, the focal position of the electromagnetic wave or the reflection direction of the electromagnetic wave is changed by moving the reflecting mirror for reflecting the electromagnetic wave oscillated from the radiant heating means. Then, the amount of radiant heat reaching the mold is controlled so as to be different between one mold and the other mold, and heating is performed while generating a temperature difference between the pair of molds. The heating device for an optical element molding die according to the invention according to claim 2 reflects an electromagnetic wave oscillated from the radiant heating means by a reflecting mirror, and a pair of molding dies and an optical element material disposed between the pair of molding dies. And heat. At this time, by changing the position or rotation angle of the reflecting mirror in the optical axis direction by the variable means, the amount of radiant heat reaching one of the molds and the other mold is changed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment of the present invention, a reflecting mirror for reflecting electromagnetic waves oscillated from a radiant heating device toward an upper mold, a lower mold and a glass material is moved forward or backward.
Alternatively, by rotating the reflecting mirror, the electromagnetic waves reflected by the upper mold and the lower mold are differentiated, and the amount of radiant heat absorbed by the mold with the smaller radius of curvature of the upper mold and the lower mold is used as the other. The upper mold and the lower mold are heated to different temperatures, and the heat transfer speed of the heat that moves from the glass filling the mold having a small radius of curvature, that is, the mold having a large cavity, to the mold having a small radius of curvature is relatively reduced. The purpose of the present invention is to reduce the uneven heat distribution generated during the cooling process of the glass optical element, thereby reducing the internal stress generated in the glass optical element.

In the embodiment of the present invention, the case where a biconvex lens is formed is taken as an example. However, there is a remarkable difference in the radius of curvature of the formed optical surface such as a biconcave lens, a meniscus lens, a plano-convex lens, and a plano-concave lens. When molding a lens that has a difference in the mold gap between the upper and lower molds,
Can be applied. The molding surface of the lens is not limited to a spherical surface, and can be applied to a case where the lens has a curved surface such as an aspheric surface, a cylindrical surface, or a paraboloid. Further, the present invention can be applied to an optical element such as a prism, in which there is a difference between the upper and lower mold cavities. Furthermore, in the embodiment of the present invention, an infrared lamp heater is used as a radiant heating unit for heating the mold and the optical element material. However, the present invention is not limited to this, and a laser light source may be used as a source of radiation as electromagnetic waves. Alternatively, a microwave generator may be used.
Hereinafter, specific embodiments will be described.

(Embodiment 1) FIGS. 1 to 6 show Embodiment 1, FIG. 1 is a longitudinal sectional view of a heating device of an optical element molding die, and FIG. Charts,
FIG. 3 is a diagram showing a heat pool of a biconvex lens according to a conventional heating method, FIG. 4 is a diagram showing a heat pool of a biconvex lens according to the present embodiment, and FIG. 1 is a sectional view taken along the line AA ′, and FIG. 6 is a sectional view taken along the line AA ′ in FIG.

In this embodiment, a case where a biconvex lens having a smaller radius of curvature on the upper mold forming surface side than the lower mold forming surface side will be described. In FIG. 1, an upper mold 1 as one of the molds is made of WC, and a molding surface 1a is mirror-finished to a spherical surface having a radius of curvature of 10 mm. The lower mold 2 as the other mold is made of WC, and the molding surface 2a is mirror-finished to a spherical surface having a radius of curvature of 100 mm. The upper mold 1 and the lower mold 2 are arranged to face each other and form a pair. A glass material 3 as an optical element material is disposed between the upper mold 1 and the lower mold 2, and the glass material 3 is made of Sumitomo Optical Glass Co., Ltd. P-SK60 (transition point 381 ° C., yield point 40).
(4 ° C.) as a material, and is preliminarily polished into a spherical shape. The upper mold 1 and the lower mold 2 are slidably fitted on the inner periphery of the sleeve 6 with the glass material 3 interposed between the molding surfaces 1a and 2a. The sleeve 6 is formed in a cylindrical shape made of SiC. The upper mold 1, the lower mold 2, the glass material 3, and the sleeve 6 are combined to form an optical element molding die and a molding set S as an optical element material.

The molding set S is placed on the upper surface of the main shaft 10 and is moved up and down to form the glass material 3 therein. A servo motor (not shown) is connected to the main shaft 10, and is driven up and down by rotation of the servo motor. A base 8 is provided on the outer periphery of the main shaft 10, and the main shaft 10 is inserted into a through hole 8 a formed in the center of the base 8. Stand 8
A quartz tube 7 is provided upright on the upper surface 8b. Quartz tube 7
Is made of a transparent quartz glass having a cylindrical shape covering the periphery of the molding set S. An upper cover 5 is fitted over the quartz tube 7 so as to cover the quartz tube 7, and a through hole 5 a for inserting the pressure rod 4 is formed in the center of the upper cover 5. The pressing rod 4 is a rod having a flat tip 4a, and is formed on a pressing rod fixing portion of a machine frame (not shown) so as to abut on the upper surface 1b of the upper mold 1 when the glass material 3 in the forming set S is formed. Fixed.

On the outer edge of the upper surface 8b of the base 8, a gas inlet 11 through which an inert gas flows is formed from above to make the inside of the quartz tube 7 a non-oxidizing atmosphere. A gas inlet pipe 12 is connected to the gas inlet 11 and is connected to a gas generator (not shown) for supplying an inert gas. A plurality of holes 8c are formed in the lower surface of the base 8, and the rod 9a of the cylinder 9 is fitted in the holes 8c. A plurality of cylinders 9 are provided to move the table 8 in the vertical direction, and are fixed to a machine frame (not shown). The cylinder 9 can adjust the vertical position of the infrared lamp heater 13 and the quartz tube 7 described later by moving the table 8 in the vertical direction.

Outside the quartz tube 7, four rod-shaped infrared lamp heaters 13 as radiant heating means are provided at four equally-spaced positions on the circumference around the axis of the molding set S. It is arranged. In FIG. 1, the illustration of the infrared lamp heaters 13 arranged at the front and back of the figure is omitted.
In the vicinity of the lower part of the infrared lamp heater 13, a fixed reflecting plate 14 as a reflecting mirror is provided. Fixed reflector 14
Are arranged to collect infrared rays as electromagnetic waves oscillated from the respective infrared lamp heaters 13 and reflect the infrared rays toward the lower mold 2. The reflecting surface 14a of the fixed reflecting plate 14 has a curved surface so as to collect and reflect infrared rays, is mirror-finished, and is coated with gold. The fixed reflection plate 14 is attached to the machine frame (not shown) in a pair with the infrared lamp heater 13.

A movable reflecting plate 15 as a reflecting mirror is disposed near the upper part of the infrared lamp heater 13, and the movable reflecting plate 15 is fixed to a reflecting plate cylinder 16 as a variable means. It is moved in the front-back direction (the direction of arrow X) by driving the use cylinder 16. Further, the movable reflectors 15 are arranged so as to collect infrared rays as electromagnetic waves oscillated from the respective infrared lamp heaters 13 and reflect the infrared rays toward the upper mold 1. The reflecting surface 15a of the movable reflecting plate 15 is
Similarly to the above, it is formed into a curved surface so as to collect and reflect infrared rays, is mirror-finished, and is coated with gold. Further, the movable reflecting plate 15 and the reflecting plate cylinder 16
Are mounted on a machine frame (not shown) in a pair with the infrared lamp heater 13.

Next, a method for heating an optical element mold using the heating device having the above-described configuration will be described. First, the upper die 1, the lower die 2, and the glass material 3 are inserted into the sleeve 6 to form a molding set S, and the molding set S is placed on the main shaft 10. Immediately before the temperature rise by the infrared lamp heater 13 is started, the molding set S on the main shaft 10 is such that the lower end of the upper mold 1 (the molding surface 1a side) is higher than the lower end of the movable reflection plate 15 and the upper end of the lower mold 2 The vertical position is adjusted so that is below the upper end of the fixed reflector 14. In addition, the movable reflector 15
And the focal point of the fixed reflector 14 are arranged on the same axis in the vertical direction. Infrared lamp heater 1
By 3, the temperature rise of the molding set S is started. At this time, as shown in FIG. 5, the infrared light reflected by the fixed reflecting plate 14 and the infrared light reflected by the movable reflecting plate 15 are focused on the same axis. In FIG. 5, the fixed reflecting plate 14 is not shown because it is positioned below the movable reflecting plate 15 so as to overlap.

As shown in FIG. 2, the temperature β of the upper mold 1 is not higher than 381 ° C., which is the transition temperature of the glass material 3.
And the temperature α of the lower mold 2 are increased at a uniform temperature. During the temperature rise, the temperature β of the upper mold 1 and the temperature α of the lower mold 2 are 300 ° C.
, An inert gas such as nitrogen gas or argon gas (nitrogen gas is used in the present embodiment) is introduced from the gas inflow pipe 12, flows into the quartz tube 7 from the gas inlet 11, and is quartz. The inside of the pipe 7 is purged so as to have a non-oxidizing atmosphere. When the temperature of the glass material 3 reaches 381 ° C., the reflecting plate cylinder 16 is driven to move the movable reflecting plate 15.
Retreat. After the retreat, as shown in FIG. 6, the focal point of the infrared light collected by the movable reflector 15 is
Is located behind the focal point of the infrared light condensed. Therefore, the infrared rays collected by the movable reflection plate 15 and reflected on the upper mold 1 side are diffused and reach the infrared rays irradiated on the lower mold 2. For this reason, the temperature rise rate of the upper mold 1 is slower than that of the lower mold 2, and the temperature α of the lower mold 2 is higher than the temperature β of the upper mold 1.

The temperature of the lower mold 2 is lower than the yield point 40 of the glass material 3.
When the temperature reaches 4 ° C. or higher, the main shaft 10 is raised and molding is started until the upper surface 1 b of the upper die 1 comes into contact with the pressure rod 4.
Since the temperature β of the upper mold 1 was lower than the temperature α of the lower mold 2 before the start of molding, the cooling rate of the glass also became higher on the upper mold side, and as shown by the hatched portion in FIG. As shown by the hatched portion in FIG. 4, the heat accumulation of the biconvex lens, which is a molded product, generated when the temperature difference between the first mold 1 and the lower mold 2 was not provided,
In the case where a temperature difference is provided between the upper mold 1 and the lower mold 2 according to the present embodiment, the size becomes smaller like a heat pool of a biconvex lens which is a molded product.

According to the present embodiment, when molding a lens having a large difference in radius of curvature on both surfaces and easy distribution of heat on glass, it is possible to heat the respective molds to different temperatures. Therefore, uneven heat distribution generated when molding the lens can be reduced. As a result, the internal stress of the molded lens is reduced, and it is possible to prevent sink marks, cracks, birefringence due to residual stress, and the like.

(Embodiment 2) FIGS. 7 to 9 show Embodiment 2, FIG. 7 is a longitudinal sectional view of a heating device of an optical element molding die, and FIG. 8 shows an initial ray trajectory in a heating process. FIG. 9 is a diagram showing the trajectories of light rays in the middle stage of the heating process. Since the heating device of the optical element molding die according to the present embodiment is mostly the same as that of the first embodiment, only different portions are shown, and the same members are denoted by the same reference numerals and description thereof is omitted.

In FIG. 7, a table 2
0 is disposed, and a through hole 20a is formed in the center of the table 20.
The spindle 10 is inserted into the shaft. The quartz tube 7 is provided upright on the upper surface 20 b of the table 20. On the outer edge side of the upper surface 20b of the base 20, a gas inlet 11 through which an inert gas flows is formed from above to make the inside of the quartz tube 7 a non-oxidizing atmosphere. The gas inlet 11 has a gas inlet pipe 12
Are connected to a gas generator (not shown) for supplying an inert gas. The base 20 is fixed to a machine frame (not shown).

Outside the quartz tube 7, an annular infrared lamp heater 21 is disposed concentrically with the axis of the quartz tube 7. Outside the infrared lamp heater 21, the infrared light oscillated from the infrared lamp heater 21 is surrounded by the inner surface of the sleeve 6 constituting the molding set S, the molding surface 1 a of the upper mold 1 and the molding surface 2 a of the lower mold 2. Four reflecting mirrors 22 for reflecting light in the vicinity of the closed space are provided. Reflecting mirror 2
Numeral 2 has a shape obtained by dividing the ring into four parts, and the radius of curvature of the reflecting surface 22a is set so as to reflect the infrared light oscillated from the infrared lamp heater 21 as parallel light.
A projection 2 as a variable means is provided on the back of the reflecting mirror 22.
The projection 23 is rotatably supported by a machine frame (not shown) so that the focal position of the reflecting mirror 22 matches the position of the ring of the infrared lamp heater 21. further,
A rotation shaft of a motor (not shown) is connected to the projection 23, and the rotation angle of the reflection mirror 22 can be changed by rotating the motor.

Next, a method of heating the optical element mold using the heating device having the above-described configuration will be described. First, the upper die 1, the lower die 2, and the glass material 3 are inserted into the sleeve 6 to form a molding set S, and the molding set S is placed on the main shaft 10. First, the reflecting mirror 22 includes the infrared lamp heater 21.
The rotation angle is set so that the infrared light oscillated from is reflected in the horizontal direction. Immediately before the temperature rise by the infrared lamp heater 21 is started, the molding set S on the spindle 10 is set.
Indicates that the infrared light reflected from the reflecting mirror 22 has the upper mold 1 and the lower mold 2
Are arranged at positions where the light is evenly reflected. The heating of the molding set S is started by the infrared lamp heater 21. At this time, as shown in FIG. 8, the upper die 1 and the lower die 2 reflect an equal amount of infrared rays.

Until the temperature of the glass material 3 reaches 381 ° C., the same steps as those of the first embodiment are performed. When the temperature of the glass material 3 reaches 381 ° C., a motor (not shown) is operated to turn the reflecting mirror 22 downward. When the reflecting mirror 22 faces downward, as shown in FIG. 9, the infrared rays reflected by the reflecting mirror 22 are largely reflected by the lower mold 2. The following steps after the pressurization are described in Embodiment 1.
Therefore, the description is omitted.

According to the present embodiment, in addition to the same effect as in the first embodiment, the amount of infrared light absorbed by each of the upper mold and the lower mold can be easily adjusted only by rotating the reflecting mirror. In addition, the required number of infrared lamp heaters and reflecting mirrors can be reduced, and the configuration of the heating device can be simplified.

The technical idea having the following configuration is derived from the above specific embodiment. (Supplementary Note) (1) In a method of heating an optical element molding die in which a pair of molding dies arranged opposite to each other and a glass material inserted between the molding dies are heated by a radiation heating device and a reflecting mirror, The electromagnetic waves oscillated and reflected by the reflecting mirror, by changing the focal position of the reflecting mirror, or by changing the reflecting direction, the amount of radiant heat reaching the forming die can be changed between one forming die and the other forming die. A method of heating an optical element molding die, wherein the heating is performed while generating a temperature difference between a pair of molding dies under different control. When molding optical elements with a large difference in the radius of curvature of both surfaces and easy distribution of heat in glass, the temperature of each mold can be heated to different temperatures, so when molding optical elements The resulting uneven heat distribution can be reduced. Thereby, the internal stress of the molded optical element is reduced, and it is possible to prevent sink marks, cracks, birefringence due to residual stress, and the like. (2) A glass material is inserted between a pair of molds arranged opposite to each other, and the glass material is heated and softened. An apparatus for forming an optical element, comprising: a reflecting mirror that changes a position or a direction of a reflecting mirror that reflects an oscillated electromagnetic wave. When molding optical elements that have a large difference in the radius of curvature of both surfaces and easily distribute heat to glass, the temperature of each mold can be heated to different temperatures, so when molding optical elements The resulting uneven heat distribution can be reduced. This reduces the internal stress of the molded optical element,
It is possible to prevent sink marks, cracks, birefringence due to residual stress, and the like.

[0027]

According to the method of heating an optical element mold of the invention according to the first aspect, when forming an optical element having a large difference in radius of curvature on both surfaces and easily forming a heat distribution on glass, Since the temperature of the mold can be heated to a different temperature, uneven heat distribution generated when molding the optical element can be reduced. As a result, the internal stress of the molded optical element is reduced, and sinks, cracks,
Birefringence due to residual stress can be prevented. According to the heating device for an optical element mold according to the second aspect of the present invention, the method for heating the optical element mold according to the first aspect can be easily performed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a heating device for an optical element molding die according to a first embodiment.

FIG. 2 is a chart showing a heating pattern of an upper die and a lower die of the first embodiment.

FIG. 3 is a diagram showing heat accumulation of a biconvex lens by a conventional heating method according to the first embodiment.

FIG. 4 is a diagram showing heat accumulation of a biconvex lens according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view taken along the line AA ′ of FIG. 1, showing a trajectory of an initial light beam in a temperature rising process according to the first embodiment.

FIG. 6 is a trajectory of a light beam after a middle stage in a heating process according to the first embodiment and is a cross-sectional view taken along the line AA ′ of FIG. 1;

FIG. 7 is a longitudinal sectional view of a heating device for an optical element molding die according to a second embodiment.

FIG. 8 is a diagram showing a trajectory of an initial light beam in a heating process according to the second embodiment.

FIG. 9 is a diagram showing a trajectory of light rays in a middle stage or later in a heating process according to the second embodiment.

FIG. 10 is a longitudinal sectional view of a conventional pressure forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper mold 1a Molding surface 2 Lower mold 2a Molding surface 3 Glass material 13 Infrared lamp heater 14 Movable reflector

Claims (2)

[Claims] 1. An optical element mold for heating a pair of molds having molding surfaces opposed to each other and an optical element material arranged between the molds by electromagnetic waves oscillated from radiant heating means. In the method, by moving a reflecting mirror that reflects the electromagnetic wave oscillated from the radiant heating unit, the focal position of the electromagnetic wave or the reflection direction of the electromagnetic wave is changed, and the amount of radiant heat reaching the mold is compared with that of the one mold. A method for heating an optical element molding die, wherein the heating is performed while controlling the temperature so as to be different from that of the other molding die and generating a temperature difference between the pair of molding dies. 2. An optical element mold for heating a pair of molds having molding surfaces opposed to each other and an optical element material arranged between the molds by electromagnetic waves oscillated from radiant heating means. In the apparatus, a reflecting mirror that reflects the electromagnetic wave oscillated from the radiant heating unit, and a variable unit that changes the position or rotation angle of the reflecting mirror in the optical axis direction, characterized by comprising: Heating equipment.